Civic Diesel Nightmare: Black Smoke & Starting Issues

Hey there! I had some similar issues with my 2002 Honda Accord diesel last year (I'd say I have some experience working on cars, but nothing too fancy). The symptoms you're describing sound really familiar, I was getting the same problems with the black smoke and cold starts. My mechanic found that the wiring harness connecting the glow control unit to the ECU was damaged and needed replacement. Total bill came to 395 Euro, but it fixed all those issues, no more black smoke, starts fine now, and the warning lights are gone. Just a heads up, I also own a Honda CR-V, and these diesels can be tricky with electrical issues. Before I can give more specific advice, Have you scanned for error codes? When was your last service? Any other warning lights showing up? Let me know these details and I might be able to help more!

Thanks for the detailed response! My Civic's at 107611 KM and just had a service last month. Yeah, I did get it scanned, throwing P0380 and P0671 codes. The mechanic cleaned the glow plugs during service but didn't replace the wiring harness, which might be the actual culprit after hearing your experience. The warning lights are just the engine light and pre-glow, nothing else showing up on the dash. Think I'll get that wiring harness checked out, seems like these older diesels have a thing for electrical gremlins! Really appreciate you sharing your fix, gives me a solid direction to look into.

Hey again! Thanks for those details about your Civic, those codes definitely ring a bell with what I experienced on my Accord. You know what's funny? My mechanic initially just cleaned the glow plugs too, but the problems came right back after a week. Those P0380 and P0671 codes are pretty much exactly what I had, they're pointing straight at the glow plug control circuit. I remember being super frustrated because I thought cleaning the plugs would fix it, but nope! Quick tip from my experience, when my mechanic finally traced the wiring harness issue, we found some spots where the insulation had worn through and was causing intermittent shorts. It was actually pretty hard to spot without really getting in there and checking every inch of the wiring. Since you've just had a service and the problems are still there, I'd bet good money it's the same wiring harness issue I had. These old Honda diesels are pretty bulletproof usually, but that wiring setup seems to be a weak point as they age. Tell your mechanic about the wiring harness, might save some diagnostic time. And hey, keep us posted on what you find! Always good to know how these things turn out.

Thanks so much for the follow-up! You've really helped me narrow this down. It's crazy how similar our issues are, right down to the same error codes! I actually just called my mechanic and mentioned the wiring harness situation you described. He agreed it's worth checking out, especially since just cleaning the glow plugs didn't solve it. Got an appointment scheduled for next week to have him trace the wiring. You're probably right about those worn spots being hard to spot, makes total sense why they might have missed it during the regular service. Really crossing my fingers it's the same issue you had, at least then I know there's a proper fix! I'll definitely update the thread once we figure it out. These electrical problems can be such a pain to diagnose, so having real experiences like yours to reference is super helpful. Thanks again for taking the time to share your experience, saved me a lot of headaches trying unusual fixes!